This invention relates to an electronic detonator and to a method of manufacturing an electronic detonator.
Typically an electronic detonator includes a tubular housing which contains a printed circuit board which carries various electronic components. An ignition element such as a bridge is provided on the board. The ignition element is exposed to a primary explosive composition which is exposed to a secondary explosive material.
To achieve reliable operation of the detonator it is inter alia necessary to ensure that the primary explosive composition is in intimate contact with the ignition element. A technique which has been adopted requires a portion of the printed circuit board, which carries the ignition element, to be located inside a bore of a tube which has opposed open ends. The printed circuit board protrudes from one end of the enclosure (the tube) and, as an initial step, this end is sealed through the use of a suitable potting mixture which also adheres to an adjacent portion of the printed circuit board. The printed circuit board and the tube are then orientated so that the remaining open end of the tube is uppermost. A suitable primary explosive, which is in particulate form, is then placed into the tube through the open upper end and is tamped in position thereby to bring the composition into contact with the ignition element. This process does, however, have some disadvantages.
Firstly, the sealing of the printed circuit board to the tube can be problematic. If the sealing is not properly done a malfunction can occur. The potting compound can also damage the electronic components on the printed circuit board.
A second aspect is that the quantity of explosive composition which is placed in particulate form into the tube may vary from detonator to detonator—a feature which can produce inconsistent outcomes. Also, the tamping of the composition around the ignition element can result in physical damage to the element.
EP1548391 describes a detonator assembly in which a printed circuit board, carrying an ignition element, is positioned partly inside a cup-shaped body. The ignition element is covered by a settable explosive composition. There is however no disclosure of any mechanism which enables the printed circuit board to be precisely and correctly positioned relative to the cup-shaped body.
An object of the present invention is to address the aforementioned aspects.